[WenetDemo] improve safety and maintainability

runtime/ios/WenetDemo/WenetDemo/ViewController.swift

@@ -25,7 +25,7 @@ class ViewController: UIViewController {
 
   var wenetModel: Wenet?
   var audioEngine: AVAudioEngine?
-  var startRecord: Bool?
+  var startRecord = false
   private var workItem: DispatchWorkItem?
 
   override func viewDidLoad() {
@@ -38,32 +38,43 @@ class ViewController: UIViewController {
   }
 
   func initModel() {
-    let modelPath = Bundle.main.path(forResource: "final", ofType: "zip")
-    let dictPath = Bundle.main.path(forResource: "units", ofType: "txt")
-    wenetModel = Wenet(modelPath:modelPath, dictPath:dictPath)!
+    guard let modelPath = Bundle.main.path(forResource: "final", ofType: "zip"),
+          let dictPath = Bundle.main.path(forResource: "units", ofType: "txt") else {
+      print("Error: Model or dictionary file not found.")
+      return
+    }
 
+    wenetModel = Wenet(modelPath: modelPath, dictPath: dictPath)
     wenetModel?.reset()
+    print("Model initialized successfully.")
   }
 
   func initRecorder() {
-    startRecord = false
-
     audioEngine = AVAudioEngine()
-    let inputNode = self.audioEngine?.inputNode
+    guard let inputNode = audioEngine?.inputNode else {
+      print("Error: Unable to access audio input node.")
+      return
+    }
+
     let bus = 0
-    let inputFormat = inputNode?.outputFormat(forBus: bus)
-    let outputFormat = AVAudioFormat(commonFormat: .pcmFormatFloat32,
-                                     sampleRate: 16000, channels: 1,
-                                     interleaved: false)!
-    let converter = AVAudioConverter(from: inputFormat!, to: outputFormat)!
-    inputNode!.installTap(onBus: bus,
-                          bufferSize: 1024,
-                          format: inputFormat) {
-      (buffer: AVAudioPCMBuffer, when: AVAudioTime) in
-      var newBufferAvailable = true
+    let inputFormat = inputNode.outputFormat(forBus: bus)
+    guard let outputFormat = AVAudioFormat(commonFormat: .pcmFormatFloat32,
+                                           sampleRate: 16000,
+                                           channels: 1,
+                                           interleaved: false) else {
+      print("Error: Unable to create output audio format.")
+      return
+    }
 
-      let inputCallback: AVAudioConverterInputBlock = {
-        inNumPackets, outStatus in
+    guard let converter = AVAudioConverter(from: inputFormat, to: outputFormat) else {
+      print("Error: Unable to create audio converter.")
+      return
+    }
+
+    inputNode.installTap(onBus: bus, bufferSize: 1024, format: inputFormat) { [weak self] buffer, _ in
+      guard let self = self else { return }
+      var newBufferAvailable = true
+      let inputCallback: AVAudioConverterInputBlock = { _, outStatus in
         if newBufferAvailable {
           outStatus.pointee = .haveData
           newBufferAvailable = false
@@ -75,12 +86,11 @@ class ViewController: UIViewController {
         }
       }
 
-      let convertedBuffer = AVAudioPCMBuffer(
-        pcmFormat: outputFormat,
-        frameCapacity:
-          AVAudioFrameCount(outputFormat.sampleRate)
-        * buffer.frameLength
-        / AVAudioFrameCount(buffer.format.sampleRate))!
+      guard let convertedBuffer = AVAudioPCMBuffer(pcmFormat: outputFormat,
+                                                   frameCapacity: AVAudioFrameCount(outputFormat.sampleRate) * buffer.frameLength / AVAudioFrameCount(buffer.format.sampleRate)) else {
+        print("Error: Unable to create converted buffer.")
+        return
+      }
 
       var error: NSError?
       let status = converter.convert(
@@ -89,55 +99,67 @@ class ViewController: UIViewController {
 
       // 16000 Hz buffer
       let actualSampleCount = Int(convertedBuffer.frameLength)
-      guard let floatChannelData = convertedBuffer.floatChannelData
-      else { return }
+
+      guard let floatChannelData = convertedBuffer.floatChannelData else {
+        print("Error: No float channel data available.")
+        return
+      }
 
       self.wenetModel?.acceptWaveForm(floatChannelData[0],
                                       Int32(actualSampleCount))
+      print("Audio data accepted by the model.")
     }
+    print("Audio recorder initialized successfully.")
   }
 
   @IBAction func btnClicked(_ sender: Any) {
-    if(!startRecord!) {
+    if(!startRecord) {
       //Clear result
       self.setResult(text: "")
 
       //Reset model
       self.wenetModel?.reset()
+      print("Model reset and result cleared.")
 
       //Start record
       do {
-        try self.audioEngine?.start()
+        try audioEngine?.start()
+        print("Audio engine started.")
       } catch let error as NSError {
         print("Got an error starting audioEngine: \(error.domain), \(error)")
+        return
       }
 
       //Start decode thread
-      workItem = DispatchWorkItem {
-        while(!self.workItem!.isCancelled) {
+      workItem = DispatchWorkItem { [weak self] in
+        guard let self = self else { return }
+        while !(self.workItem?.isCancelled ?? true) {
           self.wenetModel?.decode()
           DispatchQueue.main.sync {
-            self.setResult(text: (self.wenetModel?.get_result())!)
+            self.setResult(text: self.wenetModel?.get_result() ?? "")
+            print("Decoding in progress.")
           }
         }
       }
       DispatchQueue.global().async(execute: workItem!)
 
       startRecord = true
-      button.setTitle("Stop Record", for: UIControl.State.normal)
+      button.setTitle("Stop Record", for: .normal)
+      print("Recording started.")
     } else {
       //Stop record
       self.audioEngine?.stop()
 
       //Stop decode thread
-      workItem!.cancel()
-
+      workItem?.cancel()
       startRecord = false
-      button.setTitle("Start Record", for: UIControl.State.normal)
+      button.setTitle("Start Record", for: .normal)
+      print("Recording stopped.")
     }
   }
 
   @objc func setResult(text: String) {
     label.text = text
+    print("Result updated: \(text)")
   }
 }

runtime/ios/WenetDemo/WenetDemo/wenet/wenet.mm

@@ -83,7 +83,7 @@ - (nullable instancetype)initWithModelPath:
 - (void)reset {
   decoder->Reset();
   state = kEndBatch;
-  total_result = "";
+  total_result.clear();
 }
 
 - (void)acceptWaveForm: (float*)pcm: (int)size {
@@ -122,14 +122,15 @@ - (void)decode {
   }
 }
 
-- (NSString*)get_result {
+- (NSString *)get_result {
   std::string result;
   if (decoder->DecodedSomething()) {
     result = decoder->result()[0].sentence;
   }
-  LOG(INFO) << "wenet ui result: " << total_result + result;
-  NSLog(@"wenet ui result: %s", (total_result + result).c_str());
-  return [NSString stringWithUTF8String:(total_result + result).c_str()];
+  std::string final_result = total_result + result;
+  LOG(INFO) << "wenet ui result: " << final_result;
+  NSLog(@"wenet ui result: %s", final_result.c_str());
+  return [NSString stringWithUTF8String:final_result.c_str()];
 }
 
 @end